Speaking with io9, the "Fast and Furious" star explained that even though he's a member of the "Guardians of the Galaxy" cast, there's no reason he can't take on another Marvel role. After all, he's not actually seen on screen as Groot, since the character is completely computer generated.
"We've heard a lot of talk about Marvel wanting to have me play a character that doesn't have my voice," the actor said. "So my voice is used for Groot and my presence is used for the other character."
The statement lines up nicely with long-standing rumors that the studio has been in talks with Diesel to join the cast of "Inhumans," a movie that would most likely feature the character of Back Bolt. In the comics, Black Bolt is the king of the Inhumans, and has the power to destroy an entire city by uttering a single word. Due to this, the character is largely mute, save for the rare occasion when he is forced to display his power -- in short, a description that would sync up with Diesel's words quite nicely.
"The Last Witch Hunter" arrives in theaters October 23. Marvel's "Inhumans" is slated for theatrical release July 12, 2019.